1. Field of the Invention
The present invention relates to an electronic device, a display method thereof, and a storage medium storing a program for executing the method, and more particularly, to an electronic device having a display function which successively displays still pictures, a display method thereof, and a storage medium storing a program for executing the method.
2. Description of the Related Art
Conventional digital still cameras, as disclosed in Japanese Laid-Open Patent Application No. 11-187356, have a display unit consisting of a liquid crystal panel, or similar display panel, for displaying photographed pictures. A user who uses such a digital still camera can successively display a plurality of photographed still pictures in order to check the photographed still pictures. Some digital still cameras have a function of automatically and successively displaying a plurality of pictures for a predetermined time interval. The function is called an “album” function or a “slide show” function. Also, personal computers can successively display a plurality of still pictures.
However, the conventional technique of successively displaying a plurality of still pictures has a number of problems as described below.
The visual function of a human eye has a property called “adaptation.” Adaptation refers to how the sensitivity of human eyes changes according to the visual environment. That is, adaptation is a property allowing eyes to accommodate to their surroundings. The adaptation can be expressed as a time function, and takes place sequentially depending on changes in the visual environment.
Of the various adaptation reactions, luminance adaptation is well known. The luminance adaptation is a reaction in which the pigments of light-receiving organs of human eyes decrease while the pupils of the human eyes are dilated in a dark place, thereby allowing him or her to see objects properly with a small amount of light (dark adaptation), and in which the pigments of the light-receiving organs increase while the pupils of the human eyes are constricted in a bright place, thereby allowing him or her to see objects properly with a large amount of light (light adaptation).
Also, among the various adaptation reactions, other than the luminance adaptation, there is contrast adaptation.
In contrast adaptation, a function (a so-called “contrast response function”), representing a relationship between a contrast of a target object and a response of neural cells, is a sigmoid function. The contrast range in which a change in contrast causes a response change in neural cells is very narrow. However, since the visual cortex of the cerebrum moves the contrast range according to the visual environment, contrast sensitivity is maximized under certain visual environmental conditions.
As such, since the visual function of the human eye adapts itself to a visual environment, for example, when a digital still camera displays a still picture and a user continuously views the still picture for a predetermined time, the visual function of the user's eyes adapts itself to the brightness, contrast, etc., of the still picture so that he or she can more easily view the still picture.
If the digital still camera displays a next still picture after adaptation takes place, the user will view the next still picture in the state where a so called “bias” is applied. Accordingly, the picture viewed by the user will appear different from the picture viewed before adaptation takes place.
For example, when a user views a picture of an outdoor scene in bright weather after being subjected to dark adaptation by continuously viewing a picture showing dark night views for a predetermined time, the picture of the outdoor scene appears brighter than when he or she has not been viewing the picture showing the dark night view. On the contrary, when a user views a dark picture after being subjected to light adaptation by viewing a bright picture, the dark picture appears darker than when he or she has not been viewing the bright picture.
Likewise, considering a contrast, for example, when a user views a picture with a low contrast after adapting himself or herself to a picture with a high contrast by viewing the picture with the high contrast for a predetermined time, the picture with the low contrast appears as if it has a contrast lower than when he or she has not been viewing the picture with the high contrast. In some cases, the user cannot recognize the contrast of the picture.
Accordingly, when a plurality of pictures having low spatial correlation to each other are successively displayed for a predetermined time interval, since the visual function of a user's eyes adapts to a previous picture instead of a currently displayed picture, the displayed pictures cannot be recognized as intended by a photographer or a drafter.
Also, if a bright picture and a dark picture are alternately displayed or if a picture with a high contrast and a picture with a low contrast are alternately displayed, a user must adapt himself or herself to the corresponding picture for each alternating period, which may cause fatigue.